The preferred embodiment concerns a device for post-processing of a print substrate web printed by an electrographic printing or copying device in which toner is transfer printed onto a print substrate as a print image and subsequently fixed.
Such a device is, for example, known from the patent document EP 0 758 766 B1. There the printed print substrate web is initially guided through a fixing device. In a subsequent post-processing device, gloss and color saturation are conferred to the print image. For this, the print substrate web is first cooled after the fixing device and then directed through smoothing rollers that, for their part, are heated in order to smooth the toner in order to achieve a predominantly smooth surface. The print substrate web with the toner is subsequently re-cooled in order to feed the printed and fixed print substrate web to a subsequent end-processing (finishing).
In a further known device (U.S. Pat. No. 6,249,667) for post-processing of a print substrate web printed by an electrographic printing or copying device, a dampening or moistening device is arranged after a fixing device in the feed direction of the print substrate. A fluid film is applied on the fixed image with the dampening device, whereby a gloss dependent on the quantity of the fluid is conferred to the print image and the paper. With this dampening device, the toner is merely dampened but not smoothed.
In another known device (U.S. Pat. No. 5,694,638) for post-processing of a print substrate web printed by an electrographic printing or copying device, a controllable transport device is arranged at the print substrate output of the printing or copying device. The transport device is regulated relative to the transport speed so that a crumpling of the print substrate is prevented, since the print substrate is always held under tension. The transport device is also designed so that the print image is not influenced.
In electrographic printing, the print toner images (generated on the print substrate) of the images to be printed are fixed in the printing device and thus permanently bound with the print substrate. Such methods are sufficiently known (see, for example, US 2004/005178 A1) and are therefore not described in detail here. The fixing can thus occur in various manners, for example via roller fixing under pressure and heat or via radiation fixing under heat. With regard to the individual known techniques, reference is likewise made to the disclosure document US 2004/005178 A1 already cited before.
In the fixing, the print substrate web is exposed to heat and, if applicable, pressure, with the result that the properties of the print substrate such as, for example, dampness and sliding properties are negatively influenced. In particular, however, poor sliding properties of the print substrate can lead to the fixed toner layer being mechanically damaged or smeared in the post-processing. For post-processing, the print substrate web is therefore improved in terms of its sliding properties in the known device, in that the print substrate web is lightly dampened.
Such a dampening device is proposed in the German patent application DE 10 2004 002232.1-51 (not yet published). What is disadvantageous in this method and in the previously cited known methods is that the dampening only acts for a short time. The abrasion already noticeably increases again within a few hours. Pauses in the range of hours to days between printing and post-processing frequently occur in operation. Furthermore, the paper transport in the end processing is impaired by the slip agent lubricant. In some systems this leads to increased outage times.